Year	% of total
1971	6.535726379952591
1972	5.943254564134988
1973	11.229886350849554
1974	17.989266547406082
1975	17.724840677504005
1976	16.59054805401112
1977	17.78915867090365
1978	23.1859783453969
1979	28.320182779416065
1980	38.140331436055
1981	37.80993331445197
1982	44.10820839392268
1983	42.831895449154715
1984	44.211181781790685
1985	45.61139953606539
1986	42.87288533355101
1987	41.970445242990834
1988	28.773494621597827
1989	25.667676347726236
1990	35.230587307843905
1991	30.250079257035228
1992	34.68799770941823
1993	38.76023125893205
1994	42.415551800579784
1995	40.03879728419011
1996	32.87891398559252
1997	38.749342997040024
1998	35.71718099767605
1999	26.584811164825332
2000	32.36306377235407
2001	41.08417022693225
2002	42.44964654896807
2003	36.741280017385634
2004	30.389856736384964
2005	32.23402944327004
2006	35.510765516660584
2007	28.27072569008053
2008	25.013157461925594
2009	27.777458804616177
2010	26.81318505863663
2011	30.642584230635638
2012	27.232040817831262
2013	29.369130991242326
2014	29.607939656295695
2015	26.241575087784653